Have you ever wondered why some Collies have a luxurious mane of fur while others have a shorter coat? The answer to this lies in the fascinating world of canine genetics!
The sections are as follows:
Overview
We have often been asked what determines a collie's coat type. This can be especially confusing when you see two smooth collie parents who produce a rough puppy. To break this topic down we give you a short answer about basic genetics and we break down how exactly this works in the following.
There are two recognized Collie varieties: Rough Collie (long-haired) and Smooth Collie (short-haired). The coat type is determined by genes inherited from the parents.
Rough Collie Gene (rr): Recessive gene for a long, rough coat.
Smooth Collie Gene:
Rough Factored Smooth (Sr): Dominant gene for a short, smooth coat, but also carries the Rough Collie gene.
Pure for Smooth (SS): This Collie wouldn't carry the Rough Collie gene.
Genetics
Genetically speaking there are three types of coats a collie can be born with, visually they are identified as either roughs or smooths. These coats can be told apart by knowing that the Rough coats are long-haired, and Smooth coats are short-haired. The Smooth coat (genetically speaking) can be a Pure for Smooth OR a Rough factored Smooth.
The coat type a puppy will have will be based on their sire and dam. In all cases, the rough gene is recessive, which will be shown as [rr]. The smooth gene which is dominant; will be pure for smooth [SS] or rough factored smooth [Sr].
For example, let’s say that eye color is determined by two main genes. For this example, we will use two main eye color genes blue (b) and green (g). Blue is recessive, and green is dominant, similar to the Smooth Collie gene (carrying Rough).
Green Eyes (GG or Gg/ Smooths): People with two green genes (GG) or one green gene and one blue gene (Gg) will have green eyes.
Blue Eyes (bb/ Roughs): People with two blue genes (bb) will have blue eyes.
We use this analogy because it reflects the concept of a dominant gene (Green - Smooth Collie) also carrying the recessive trait (blue - Rough Collie).
Here's the example scenario in action:
Two Smooth Collies (green eyes/ dominant gene, but carrying the recessive gene) can have Rough Collie puppies (if they both pass on the recessive gene).
While this is not a perfect analogy, due to the presence of additional genes in real eye color, this example highlights the key concept of dominant genes potentially carrying recessive traits, similar to how Smooth Collies (dominant gene) can carry the Rough Collie gene (recessive).
To better visualize how these genes get passed down please refer to our Punnett square below (for this example we used a rough parent [rr] and Pure for Smooth parent [SS].)
Terminally used:
SS (Pure for Smooth)
Sr (Rough factored Smooth)
rr (Rough)
Another example below shows a common genetic pairing of two rough factored smooths.
In the Punnett square above we can see that statically, we would have a litter of 25% SS (Pure for Smooth) 50% Sr (Rough factored Smooth), and 25% Rr (Rough) based on the parents' coat types.
Conclusion
Understanding Collie coat genetics might seem complex at first, but by breaking it down, we hope you can appreciate the fascinating interplay of dominant and recessive genes that creates the Rough and Smooth Collie variations.
Whether you're a longtime Collie lover or simply curious about the breed, this series on "What a Collie Is" aims to provide valuable insights into these magnificent dogs.